1. Field of the Invention
The present invention relates to a composition for an ultrasonic probe and a silicone resin for an ultrasonic probe.
2. Description of the Related Art
A probe for ultrasound diagnostic apparatus (also referred to as an ultrasonic probe) includes a piezoelectric element transmitting/receiving ultrasonic waves, and an acoustic lens which is a portion brought into contact with a living body. Ultrasonic waves generated from the piezoelectric element are incident on a living body by being transmitted through the acoustic lens. If the difference between acoustic impedance (density×acoustic velocity) of acoustic lens and acoustic impedance of a living body is large, ultrasonic waves are reflected on the surface of the living body. Therefore, the ultrasonic waves are not effectively incident in a living body, and thus, it is difficult to obtain high resolution. For this reason, it is necessary to reduce ultrasonic attenuation by matching the acoustic impedance of the acoustic lens and the acoustic impedance of the living body.
Accordingly, a silicone resin which is close to acoustic impedance (1.4 to 1.7×106 kg/m2·sec) of a living body and of which ultrasonic attenuation is small has been mainly used as the material of the acoustic lens.
For example, in JP1996-305375A (JP-H8-305375A), a composition, which is formed of a silicone compound having a diorganopolysiloxane as a main agent and another kind of an organopolysiloxane, is proposed as a composition for an acoustic lens. There is a disclosure that, with use of this composition, it is possible to bring the acoustic impedance to a living body and to form an acoustic lens of which ultrasonic attenuation is small in a high frequency region and which has high resolution.
In addition, in JP2013-199513A, a composition containing a vinyl group-containing linear organopolysiloxane, a linear organohydrogenpolysiloxane, a specific vinyl group-containing branched organopolysiloxane, and an inorganic filling material is proposed as a silicone resin composition. There is a disclosure that it is possible to obtain a silicone rubber member capable of withstanding large deformation by cross-linking a vinyl group and a Si—H group through a hydrosilylation reaction and making the molecular weight large.